The present invention relates broadly to a thermal test fixture, and in particular to a thermally controlled T/R module test apparatus.
The state of the art of thermally controlled test apparatus is well represented and alleviated to some degree by the prior art apparatus and approaches which are contained in the following U.S. Patents:
U.S. Pat. No. 3,321,953 issued to Roveti on 30 May 1967; PA0 U.S. Pat. No. 4,172,993 issued to Leach on 30 Oct. 1979; and PA0 U.S. Pat. No. 4,324,285 issued to Henderson on 13 Apr. 1982.
The Roveti reference discloses an apparatus for thermal testing transistors in situ comprising a generally pistol-shaped housing supporting at the muzzle end a fixed hook-shaped member and a movable hook-shaped member surrounding a transistor. This adjusts the turns ratio of the transformer and determines the amount of current which will flow through the members. The push button is then depressed until the contacts are closed to energize the transformer. Current flows through the members heating them. Of course, the members may be indirectly heated by imbedded heating elements, if desired. As the members and the transistor heat, the current flowing through the thermistors changes, and these changes are shown on the meter. When the temperature of the system including the transistor has stabilized, as shown by no further changes in the reading of the meter, the transistor and the circuit in which it is connected is tested for operation by injecting a signal (shaped pulse or otherwise) into the input of the system containing the transistor, and observing the size and shape of the signal at the output of the system. The effects of temperature can thereby be seen.
The Leach reference describes an environmental hood for testing printed circuit cards. In order to permit probing access to a printed circuit board while the printed circuit board is under test in a cold controlled environment, a doubled walled environmental hood is provided, the inner and outer walls spaced apart by rings containing orifices therein, a probe hole formed in the center of the ring and the outer wall cut away in the area of the ring, with a cold gas supplied to the inside of the inner wall and a hot gas supplied to the space between the walls, whereby the hot gas escaping through the orifices in the rings will raise the temperature of the cold gas, escaping from the probe hole to prevent frosting and permit viewing of the printed circuit board under test for probing.
The Henderson patent illustrates an apparatus for heating and cooling devices under test which comprises a high temperature probe and a low temperature probe, with each probe adapted to make thermal contact with a microelectronic device under test for sequentially heating the device first to a preselected high temperature and then cooling the device to a preselected low temperature. A control system is provided, connected to each of the probes by a small diameter, flexible cable. Each probe is a small, box-like structure having a heat sink, and a heat-sensing diode embedded in the heat sink. The control system senses the heat sink temperature and controls current through the heater to maintain the heat sink at a preselected temperature. The high temperature probe is placed on the top surface of a device under test and serves to add heat quickly thereto to bring the device to a preselected temperature above ambient. The low temperature probe includes a reservoir in contact with its heat sink for holding chips of dry ice, and when the latter probe is placed on the top surface of a device under test, the sublimating dry ice removes heat from the device. The heater portion of the low temperature probe serves to add heat to its heat sink when the device tends to become cooler than a preselected below-ambient temperature. An indicator is utilized to read the heat sink temperature of the probe in use at a given instant.